The “vmlinuz-4.18.12-041812-generic has invalid signature” error is a common issue encountered by many Ubuntu users, particularly those running a dual-boot system. This error typically arises when trying to boot with an upgraded kernel. This article will guide you through the steps to resolve this error.
Understanding the Error
The error message “vmlinuz-4.18.12-041812-generic has invalid signature” is related to the Secure Boot feature in your system’s BIOS/UEFI settings. Secure Boot is a security standard developed by the PC industry to help make sure that your PC boots using only software that is trusted by the PC manufacturer. When Secure Boot is enabled, it’s harder for malware, such as rootkits and bootkits, to infect your system.
However, Secure Boot can also prevent your system from booting if it detects unsigned or invalidly signed kernels, such as the custom kernel “vmlinuz-4.18.12-041812-generic” in this case.
Solution 1: Sign the Kernel Yourself for Secure Boot
The first solution involves signing the kernel yourself. This is a complex process and should be undertaken with caution. Be sure to backup your /boot/EFI directory before proceeding.
Step 1: Create a Signing Key
First, you need to create a Machine Owner Key (MOK) pair, which includes a private and a public key. Use the openssl command to generate the keys:
openssl req -new -x509 -newkey rsa:2048 -keyout MOK.priv -outform DER -out MOK.der -nodes -days 36500 -subj "/CN=Descriptive common name/"This command generates a new RSA key pair, with the private key (MOK.priv) and the public key (MOK.der), which will be valid for approximately 100 years.
Step 2: Enroll the Key to Your Shim Installation
Next, you need to enroll the public key to your shim installation. Use the mokutil command to do this:
sudo mokutil --import MOK.derThis command imports the public key into the MOK database. Upon the next reboot, you’ll be asked to enroll the key. Follow the on-screen instructions to complete the process.
Step 3: Sign the Installed Kernel
Finally, you need to sign the installed kernel using the sbsign command:
sudo sbsign --key MOK.priv --cert MOK.der --output /boot/vmlinuz-4.18.12-041812-generic /boot/vmlinuz-4.18.12-041812-genericThis command signs the kernel with the private key, making it recognizable by Secure Boot.
Solution 2: Disable Secure Boot in the BIOS/UEFI Menu
If the first solution seems too complex or risky, you can choose to disable Secure Boot in your system’s BIOS/UEFI settings. This is a simpler solution, but it may not be ideal for those who want to keep Secure Boot enabled for security reasons.
To disable Secure Boot, restart your computer and press the key to enter the BIOS/UEFI menu (this key varies depending on your device). Look for the Secure Boot option and disable it, then save and exit.
Solution 3: Use a Signed, Generic Kernel from Your Distribution
If neither of the above solutions is viable, you can opt to use a signed, generic kernel provided by your distribution. This option may not be available for everyone, but it’s worth checking if it applies to your situation.
In conclusion, the “vmlinuz-4.18.12-041812-generic has invalid signature” error can be resolved by either signing the kernel yourself, disabling Secure Boot, or using a signed kernel from your distribution. Always remember to take a backup before making any changes to your system.
Secure Boot is a security feature in your system’s BIOS/UEFI settings that ensures your PC boots using only trusted software, as verified by the PC manufacturer. It helps protect against malware and unauthorized software from infecting your system.
This error occurs when the Secure Boot feature detects an unsigned or invalidly signed kernel, such as the custom kernel "vmlinuz-4.18.12-041812-generic" in this case.
Yes, you can fix the error by signing the kernel yourself. However, this process can be complex and should be done with caution. It involves creating a signing key, enrolling it to your shim installation, and signing the installed kernel with the key.
Yes, if signing the kernel yourself seems too complex or risky, you can choose to disable Secure Boot in your system’s BIOS/UEFI settings. This is a simpler solution, but keep in mind that it may not be ideal for those who want to keep Secure Boot enabled for security reasons.
If neither of the above solutions is viable, you can check if your distribution provides a signed, generic kernel that you can use instead. This option may not be available for everyone, but it’s worth checking if it applies to your situation.
